Investigators were preparing Wednesday for a second day of searching inhospitable Alpine mountainsides for more clues to what caused a German medium-haul jetliner to fall out of the sky over southern France in the span of just eight minutes.

The Germanwings Airbus A320 operated by Lufthansa was less than an hour from completing its scheduled flight to Dusseldorf from Barcelona Tuesday morning when it unexpectedly went into a rapid descent from its cruising altitude of 38,000 feet to around 6,000 feet. French officials have said that it ...